package com.fengyunhe.utils.ip;

import java.io.UnsupportedEncodingException;
import java.util.StringTokenizer;

public class IpUtil {

  /**
   * 从ip的字符串形式得到字节数组形式
   * 
   * @param ip
   *          字符串形式的ip
   * @return 字节数组形式的ip
   */
  public static byte[] getIpByteArrayFromString(String ip) {
    byte[] ret = new byte[4];
    StringTokenizer st = new StringTokenizer(ip, ".");
    try {
      ret[0] = (byte) (Integer.parseInt(st.nextToken()) & 0xFF);
      ret[1] = (byte) (Integer.parseInt(st.nextToken()) & 0xFF);
      ret[2] = (byte) (Integer.parseInt(st.nextToken()) & 0xFF);
      ret[3] = (byte) (Integer.parseInt(st.nextToken()) & 0xFF);
    } catch (Exception e) {
      e.printStackTrace();
      // LogFactory.log("从ip的字符串形式得到字节数组形式报错", Level.ERROR, e);
    }
    return ret;
  }

  /**
   * @param ip
   *          ip的字节数组形式
   * @return 字符串形式的ip
   */
  public static String getIpStringFromBytes(byte[] ip) {
    StringBuilder sb = new StringBuilder();
    sb.append(ip[0] & 0xFF);
    sb.append('.');
    sb.append(ip[1] & 0xFF);
    sb.append('.');
    sb.append(ip[2] & 0xFF);
    sb.append('.');
    sb.append(ip[3] & 0xFF);
    return sb.toString();
  }

  /**
   * 根据某种编码方式将字节数组转换成字符串
   * 
   * @param b
   *          字节数组
   * @param offset
   *          要转换的起始位置
   * @param len
   *          要转换的长度
   * @param encoding
   *          编码方式
   * @return 如果encoding不支持，返回一个缺省编码的字符串
   */
  public static String getString(byte[] b, int offset, int len, String encoding) {
    try {
      return new String(b, offset, len, encoding);
    } catch (UnsupportedEncodingException e) {
      return new String(b, offset, len);
    }
  }
}
